1. Field of the Invention
The present invention relates to an axial gap type generator that is mounted on an engine, and more particularly, to an axial gap type generator in which gaps between stator cores and a rotor yoke can be set with satisfactory precision.
2. Description of the Related Art
For general-purpose engines or the like for industrial use, there is known a configuration in which a generator is connected with one end of a crankshaft protruding out of an engine main body.
For instance, a technique disclosed in Japanese Unexamined Patent Application Publication (JP-A) No. H10-4650 provides magnets for power generation at a flywheel that is fixed to the crankshaft end of a motorcycle engine, and coils for power generation, the coils being fixed to the engine at sites that oppose the magnets in the radial direction.
Furthermore, in recent years, the use of an axial gap type generator has been proposed for compact generator configurations. In the axial gap type generator, stator cores that are fixed to the engine and are provided with power generation coils, and rotor yokes that are provided with magnets for power generation and rotate together with a crankshaft are disposed opposing one another in the center axis direction of the crankshaft.
For instance, in an axial gap type generator disclosed in JP-A No. 2009-216014, a stator core fixed to an engine is disposed in a spacing between a pair of rotor yokes that protrude from a crankshaft towards the outer diameter side and are spaced apart from each other in the axial direction.
Also, in an axial gap type generator disclosed JP-A No. 2010-038006, protrusions that are integrally formed with a stator are directly connected with a support member on the side of an engine, thereby enhancing the positioning precision of a stator core with respect to the engine.
In axial gap type generators such as those described above, the efficiency of the generator depends on the axial-direction gap between a stator core and a rotor yoke. Therefore, it is important to set the gap with satisfactory precision.
However, the axial-direction positional relationship between a crank case on which the stator core is mounted and the crankshaft on which the rotor yoke is mounted exhibits unavoidable variability on account of the influence of dimensional tolerances of the various parts.
In the cases where, as a result of such influence, the rotor yoke becomes offset, in the axial direction, with respect to the position at which is should stand, the power generation efficiency drops accompanying changes in the gap of the generator.